Detailed testing will be carried out on the test sample both in Ireland and in Britain.

The man is said to be 'relatively well' and will be contacted at his home on a daily basis by public health doctors.

Minister for Health Mary Harney has said that people should not panic.

Speaking upon her return from a Council of European Health Ministers meeting in Luxembourg this evening, the Minister said she had full confidence in the medical expertise in Ireland to deal with the situation.

Ms Harney said a stock pile of anti-viral drugs capable of treating between 47% and 50% of the population was available and this is high by international standards.

She said it was likely the Irish case of the virus would be positive and wished the man in question, who is in his 20s, well.

Dr Darina O'Flanagan of the Health Protection Surveillance Centre said the man has had very few contacts with other people.

However, people on the flight on which the man returned to Ireland have not been given anti-viral testing. It is understood this is because he was not deemed to be infectious at that time.

According to the World Health Organisation, there are now confirmed or probable cases of swine flu in a total of 15 countries.

EU health ministers are meeting in an emergency session today to discuss the growing threat posed by the spread of the virus.

Last night the WHO raised its alert level to five, meaning the world is at imminent risk of a pandemic, but in a statement today it said there was no plans yet to raise it to level six.

However a senior EU official has said a travel ban to Mexico or the US was not something the European Commission would propose, preferring instead to caution travellers to be more prudent.

In Mexico, President Felipe Calderon has told citizens to stay home for a five-day partial shutdown of the economy.

In his first televised address since the crisis erupted last week, President Calderon told Mexicans to stay home with their families.

The country will suspend non-essential work and services, including some government ministries, from 1-5 May.

Mexico has reported another 17 deaths potentially linked to swine flu, bringing the total to as many as 176.

However only eight deaths are confirmed to have been linked to the virus, seven of those in Mexico.

In Britain, three more people have been diagnosed with swine flu bringing to eight the total number of people who have been confirmed with the disease there.

Yesterday evening US President Barack Obama, whose country has recorded the only death from swine flu outside Mexico, said there was no need for panic and rejected the possibility of closing the border with Mexico.

‘At this point, (health officials) have not recommended a border closing,’ he said. ‘From their perspective, it would be akin to closing the barn door after the horses are out, because we already have cases here in the United States.’